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VoIP and Number Portability: Perceived v. Real Problems
Tom Kershaw
Vice President, VoIP
VeriSign
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Agenda
Background
Circuit Switched Number Portability
Addressing and Portability on the Internet
Addressing and Portability for Wireless Data
A Parallel: H.323 and SIP
Key Portability Issues Today
Portability Architectures for VoIP
Portability Architectures for MMS
Recommendations, Bold Statements, Misc. Controversy
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Portability and the PSTN
Portability is based on regulatory mandate – Communications Act of 1996
Technical Approach is based on “PSTN” concepts such as:
Rate centers
LATAs
Lines
Hence, the LRN
Mobile has followed this model in portability and roaming, which uses TLDNs in much the same way as LRNs
LRNs do little more than tell the network what trunk group to use to get to the subscriber
What if you don’t have trunk groups, rate centers and geography?
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Portability and the Internet
Internet addressing introduces clear separation between Name Space and “Address”
Users are identified by URLs and Domain Names
Hence, the DNS constellations that provides root addressing for the Internet:
Tree-based
Highly resilient
Segmented Address Structures:
tomkershaw verisign com@ .
Address space controlled and administered by the name owner – you can have any unique address within this
domain
Address space administered by Registrars; any
unique address can be registered within
each TLD
Administered by the
industry/go-vernment
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Portability and the Internet
Namespace on the Internet maps to a network address ie [email protected] to 111.11.11.1
Names are segmented:
If I want to change my name – [email protected], I have three choices:
Change the TLD ie [email protected], assuming it is available
Change the domain to a new owner/name ie [email protected]
I can “port” my namespace into a new domain, assuming it’s available in that domain, but “tomkershaw” is not globally unique.
Address space is assumed to be infinite.
Names are fully geographic, Addresses Change Dynamically
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Service Application
Portability and ENUM
DNS+1 703-948-3345
5.4.3.3.8.4.9.3.0.7.1.e164.arpa
page:18005551234Pager
http://insite.VeriSign.comHTTP
tel:+17039483345TEL
smtp:[email protected]
Service AddressProtocol
To port this number, I can map the LRN to a SIP URI/:mailto:, or…..
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3
2
Set of NAPTR RRs
Change the domain space in the routing record…..
ENUM uses DNS to resolve internet namespaces for VoIP
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The Fork in the Road
PSTN
VoIP
Path 1: Adapt current PSTN system to IP
Path 2: Create an Entire New
System Optimized for
IP
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The Fork in the Road
PSTN
VoIP
H.323SIP
•Quickest path to market
•Non-Disruptive
•Phased Migration
•Expensive
•Difficult to Integrate with IP
•“Voice is special….”
•Slower to market
•Built to last – not a corner cutter
•Lacks features of original for some time
•Wins in the End
Portability Scenarios for VoIP
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Scenarios for Number Portability
1) PSTN to PSTN (we have this sorted out)
2) PSTN to IP
3) IP to PSTN
4) IP to IP
5) MMS to MMS (MMSC to Handset)
Bold Statement #1: Scenario 2 is the most important issue for VoIP operators today
Bold Statement #2: Scenario #5 is the most important issue for mobile operators today
Don’t Mix the Two Up
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Exec Summary (the Punch Line)
Currently, the biggest issue for VoIP Portability is introducing geographic portability
All other issues are minor in comparison
This must be addressed by the industry for VoIP to take off
Lack of geographic portability seriously hampers voip and also means most voip operators will not support portability at all
Until this is solved, other discussions are moot
The NPAC should be used for calls to or from the PSTN
IP addressing mechanisms such as ENUM and private trees should be used for IP to IP
I and P are the two most important letters in VoIP
Number portability should be implemented as a change to a resource record in ENUM/Location Server
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Key Points
Current industry discussions on “Implementing Portability for VoIP” have nothing to do with VoIP
VoIP operators did not ask for this
VoIP operators don’t benefit
VoIP operators need geographic portability, not URIs in the NPAC
The Real driver for these initiatives is MMS
When an MMS is received by an originating MMSC, it needs to find the terminating MMSC
In non-ported case, number is mapped to a carrier (easy)
In ported case, the LRN needs to map to a mailto: address
This is a very REAL problem that needs to be solved
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Geography and VoIP
VoIP separates the access network from the address
Access network can physically be anywhere; if you are on the network you are addressable
Similar structure to mobile – needs to have similar functionality
With recent FCC rulings, structure of telephone addressing will change
Rate Centers, City Codes, and NPAs will cease to be relevant
City Codes already losing relevance
DIDs will be available on demand, from anywhere, to anyone
Potential for anarchy……
…..but that’s how the Internet works
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My “Address” in VoIP
Home(VA)
Cable modem
My Phone Numbers:703-576-3287 650-834-8986248-232-9534 214-989-4587
Friend(Dallas)
Office(Mt. View)
Family(Detroit)
Local(VA)
My Service Provider(Hawaii)
IP Network
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The Geographic Portability Problem 1) Subscriber living in Washington DC
(202-222-1234) ports her number to IPCarrier; also buys a second line with phone number 415 because her son
has moved to San Francisco
2) Calls from PSTN to 202-222-1234 are “local” under tarifing rules
3) Subscriber moves across the river to Virginia; changes DSL provider but keeps VoIP provider and same phone
numbers
4) Subscriber is offered better deal by a mobile operator that combines fixed and mobile into
one package
5) Subscriber: Can’t port original number to new operator unless it has IMTs in the same rate center as 202-
222-xxxx
Can only port 408 number to a new carrier she does not even know
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Portability and VoIP to VoIP
When there are 10 million VoIP lines in North America, ¼% (.0025) of calls will be VoIP to VoIP
One of the big concerns of VoIP operators is reducing network round trips
Most peering architectures will map a phone number to:
A URI
An IP Address (typically of a proxy or border element)
The IP query will take place before a call is sent to the PSTN
The IP query may call out to an LNP resource
or the owner of the number will be up-to-date without querying the NPAC data
If a number is VoIP to VoIP, why call out to two databases when you can do portability and addressing in one?
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Simple Peering Architecture
PSTN
MediaGateway
CallCallAgentAgent
DirectorySIP/ENUM
ServiceBroker
Inter-CarrierSettlement
(??)
SubscriberPortal
ASP Domain
Applications/Services
Operator A
CallCallAgentAgent
CMTSCMTS
CallCallAgentAgent
DSLAMDSLAM
Enterprise B
IP CoreBorder
ElementBorder
Element
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An IP-to-IP Addressing Flow
SIP Redirect Engine ENUM/DNS
Interface to CCE
External Callouts(SIP or ENUM)
Number Analysis and Normalization (e.164 or URL)
TN Discovery
TN Exists?
Yes=BE RouteList
ExternalCalloutEngine
*LNP*CNAM*Carrier Select (ENUM or SIP)
Route Engine TN To BE Route List Proportional Route Splay Route ToD/DoW Engine Class 4 Route Default (Trunk Group, PSTN Ctvty)
Route Propagation: TGREP/TRIP/Manual ProvisioningPort the number
here
Or call out to an external
directory
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Addressing in VoIP: The Internet Way
Tier 1 ENUM
Or Private Peering
Misc. IP Network
Location Server/Registrar
Tier 2 ENUM
Call Control
Call Control
Call Control
Call Control
IN NAPTR 10 10 "u" "E2U+sip" “!^.*$!sip:[email protected]!”
Ported to
IN NAPTR 10 10 "u" “E2U+mailto" “!^.*$!mailto:[email protected]
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Porting in an ENUM Environment
ENUMENUMDNSDNS
Portability RequestPortability [email protected];[email protected];
[email protected]@verisign.com
Portability RequestPortability [email protected];[email protected];
[email protected]@verisign.com
RRP | EPP
Domain changed; Number Domain changed; Number “ported”“ported”
Domain changed; Number Domain changed; Number “ported”“ported”
DNS/ENUM Resolver Interface
page:18009483258Page
http://www.VeriSign.comHTTP
tel: +1 703 948 3258TEL
Smtp:[email protected]
SMTP
Service Address (NAPTR RRs)Protocol
fax: +1703 421 8233Fax
In: 8.5.2.3.8.4.9.3.0.7.1.e164.arpaOut: NAPTR RRs
ENUM is a standard translation mechanism defined by the IETF that uses DNS to convert an E.164 telephone number into a set of addresses.
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Extending the Model: Whois for VoIP (IRIS)
DNS
Option 1
Location Server/Registrar
Tier 2
ENUM
Call Control
Call Control
Call Control
Call Control
IN NAPTR 10 10 "u" "E2U+sip" “!^.*$!sip:[email protected]!”
IN NAPTR 10 10 "u" “E2U+mailto" “!^.*$!mailto:[email protected] Resources
WhoIs?
Option 2
Option 3
Perimeter Security and Interop Resources
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Models for MMS
Mobile operators have a different problem:
Since endpoints do not have IP addresses, they will be ported with LRNs
When a discovery takes place, they want a mapping of the phone number or LRN to a mailto: address
Mailto address will correspond to an MMSC in the destination network
Using this method eliminates the overhead of using the SS7 network and makes delivery more efficient
Requires an up-to-date mail to address database
This problem space is small (100 mobile operators x 3000 LRNs x 2 mailtos
Private no/low cost solutions already out there for this
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Conclusions
Biggest portability issue for VoIP carriers is geographic portability
This will become an increasingly focal issue
VoIP operators do not benefit from extending LNP infrastructure to URIs or IP addresses in the immediate term
Requiring a second dip to an external directory does not make sense – support E.164 portability directly on the IP network
Mobile operators do have a strong need for an LRN to mailto solution – and there are solutions out there
We must be very careful in our architectural decisions – the impacts are far reaching and in some cases we are solving problems before they manifest themselves
In VoIP, E.164 is a NameSpace, not an Address – need to treat it accordingly
